The counterfeiting of coins (e.g., monetary currency and tokens) and other metal objects is an ongoing problem. (Coins may also be referred to herein as “coinage.”) Many measures have been put into place to increase the difficulty with which coins can be counterfeited. This includes complex three-dimensional patterning on surfaces of the coins.
Other types of currency, such as bank notes, often include certain security features. These security features may include metallic strips, watermarks, holograms, fluorescent markers, optically variable inks, complex printed patterns, and embossing. However, it is more difficult, or impractical, to include similar security features in coins.
Coins are typically produced by mechanically stamping (also referred to as striking) a metal disc (or blank), to form a three-dimensional pattern on the disc, which provides the coin with its identity and denotes its value. Some recent methods of producing coins involve providing a coin blank, typically of a less expensive metal, and plating (e.g., electroplating or electroless plating) metals of higher value onto the coin blank. The plated coin blank can then be struck to form the final coin. For any security feature to be incorporated into such a coin, it should not affect the patterning of the coin, including the quality of its finish (of its plated surface), nor its structural integrity. The incorporation of a security feature into a coin should also be reasonably economical to avoid increasing the cost of coin production to unacceptable levels. The functioning of any security feature should also ideally last and remain sufficiently constant for the entire duration that a coin is in commercial (e.g., public) circulation, which in many cases is a number of years.